The logarithm of a number N is equal to the number L that a number B, which is called the base of the particular logarithmic system, has to be raised to to obtain the number N.

In other words, `L = log_B N`

=> N = B^L

Logarithms were invented by John Napier in the early 17th century. These are very useful in mathematical calculations involving large numbers. Using logarithms the multiplication of numbers can be accomplished by adding their logarithms and division of numbers can be accomplished by subtracting their logarithms. Also, large powers of big numbers can determined approximately.

A logarith is the exponent to which a specified base is raised to obtain a given value. You find a logarith by an inverse operation that undoes raising a base to an exponent. You can write an exponential equation as a logarithmic equation. The base of the exponent becomes the base of the logarith.